Power steering gear



July 6, 1954 w. K. cREsoN ETAL 2,682,778

PowER STEERING GEAR 2 Sheets-Sheet l Filed July l5, 1950 July 6, 1954 Filed July 15, 1950 W. K. CRESON ET AL POWER STEERING GEAR 2 Sheets-Sheet Patented July 6, 1954 vUNITED STATES ATENT OFFICE POWER STEERING GEAR poration of Indiana Application July 15, 195o, serial No. 174,698

' 'I'his invention relates to power-operated steering gears, and more particularly to that type of power-operated steering gear in which the power is not applied until the steering effort increases to some denite predetermined value. It

has heretofore been proposed to produce such a steering gear by interconnecting the manually operated steering shaft and the dirigible wheels through a speed-reducing mechanism embodying a rotatable cam or screw-threaded element and by employing axial vdisplacements of such element against a yielding resistance to control the application of power. Usually, the power-applying mechanism has been of the hydraulic type and controlled by a valve which in turn was controlled by axial displacements of the cam or screw-threaded member.

It is an object of this invention to simplify and improve the construction of such steering gears. Another object of the invention is to produce a steering gear which will possess an increased flexibility of installation and arrangement. Still another object of the invention is to facilitate the adjustment of the valve mechanism controlling the application of hydraulic power in a power-operated steering gear.

In carryingout the invention in its preferred form, we employ a housing from which is supported a rock shaft adapted for connection to dirigible wheels of a vehicle. The rock shaft is operatively connected to a helical cam mounted Within the housing for manual rotation and for limited axial movement. Yielding means'bias the cam to a normal position from which it may be displaced by loads exceeding a predetermined vallue. Exteriorly of the housing and supported therefrom are a hydraulic motor and a control valve therefor, the former operatively connected to the rock shaft and the latter connected to the cam to be operated by axial cam-movements.

With respect to the arrangements employed to mount the motor and valve on the housing, the housing is made symmetrical about a plane which extends axially of the rock shaft and normally to the cam-axis, so that the hydraulic motor and the valve can be mounted on either side of the housing, as desired. The valve, which is desirably of the open-center type, embodies a rerciprocable valve member located within a stationary, ported sleeve, and the lands on the valve and the ports in the sleeve are so located from finished end surfaces of the valve and sleeve that when those end surfaces are flush with each other the valve will be accurately centered within the sleeve. l

15 Claims. (Cl. 74-388) The accompanying drawings illustrate the invention: Fig. 1 is a side elevation, in partial section, of the steering gear with the housing-cover removed; Figs. 2, 3, and 4 are fragmental sectional views similar to Fig. 1 but on larger scales; Fig. 5 is a section on the line 5-5 of Fig. 1; Figs. 6 and 7 are views similar to Fig. 2 but illustrating modied constructions; and Fig. 8 is a fragmental view similar to Fig. 5 illustrating another modification.

The steering gear shown in Figs. 1 to 5 embodies a housing IIJ having an open side adapted to be closed by a removable cover II. In the central portion of the housing there is provided a bearing for the reception of a rock shaft I2 which extends outwardly through the closed side of the housing and has secured to its outer end an arm I3 (Fig. 5) adapted for connection to the dirigible wheels of the vehicle in which the steering gear is to be embodied. Above the rock l I8 operatively connected to both the piston-rod head I4 and the cam I'I, as more fully set forth below.

The cam I'I is'provided with a helix-like groove 2G which receives a frusto-conical stud 2I mounted on the lower end ofI the arm I8. The upper end of the arm I8 is provided with a parallelsided notch 22 which slidably receives a block 23 mounted on and rotatable relatively to a pivot pin 24 which projects laterally from the pistonhead I4. To hold the pin 24 in place in the head I4, it may be grooved as shown at 25 in Fig. 5 for the reception of a screw 26 mounted axially in the head I4; and to preserve the desired parallel relationship of the pin 24 and rock shaft I2, the head I4 may be provided with longitudinally extending grooves which receive keys 21 rigid or integral with the housing I The cam I'I is provided at its ends with hubs 30 and 3| rotatably received in aligned openings 32 and 33 in opposite side walls of the housing I0. Desirably, the cam-hubs are supported through anti-friction bearings including outer races 34 which are axially slidable in the openings 32 and 33, respectively. Means now to be 55 described resiliently locates the cam I'I in a nordished washer reacts, and a split spring ring it at the outer face of the washer 31. Each cam hub is formed with an annular groove providing an inwardly facing shoulderS'Slagainst which the ring bears to provide a removable abutmentI limiting outward axial movement of the lwasher' 31. The parts are so constructed and arranged" that, when assembled, the dished washer. 35 will be stressed and will bear with a predetermined invvardy directed force against the race 34.

The assembly of the cam and' cam-locating means is positioned axially of itself in thehousing' l0 by providing the latter with abutments which bear against the outer faces of the Washers 3-1'1 As shownv i-ny Fig. 1, one of those al'autmentsi tha-t adjacent thecarne-hub 3 I, is in the form of a spacing collar 4l] held in place in thelopening 33 by a cap Iii` removably` secured to the outer face of the housing I0, while the other constitutes a pilot portion 42 of a sleeve 43T, such sleeve having anv integral attaching flange through which it is secured to the housing i9- with the pilot 42 receivedl in the'opening 32" and the-boel of the sleeve extending 'outwardly in co-axial relationshipwith the,` cam iT.

The' cam-hub 3i! proj ects into the sleeve' 43 and is provided with an' axial hole splined for the reception of a manually rotatable steeringV shaft 45 enclosed within the conventional'tubular steering column 4B. Nea-r the outer end of the sleeve 43 there are provided` bearings 4"'1, preferably of the anti-friction type, for thes-teerin-g shaft 45. A capY 43 secured to the outer end of the sleeve 43 is adapted for attachment to the steering column 45.

In alignment with the guide-way for the pistonrod: head I4, the side tva-lly of the housing l is provided with amachined openingl receiving a pilot 5e of al cylinder head`v Eil'. The body of the cylinderv head iii' is adapted tobereceived within a hydraulic cylinder 52 which slidably receives a piston 53 mounted on the end of the piston rod I5; For the purpose of securing the cylinder 52 and: cylinder head Si in position'on the housing I0, we may employ a circular collar `54 which surrounds the end ofv the cylinder 52 and is counterbored ior the reception or" a split spring ring A disposedin an annular groove in the outer surface of the cylinder 52; An outwardly projecting annular ange ES; on' the cylinder head 5l is received between the outer surface of the housing I9 and the adjacent end' of the cylinder 52, so that when the collar 54 is urged toward the housing Il?, as by means of the screws 51, the flange 55 will be clamped betvveen the end of the cylinder and the face of the housing H3; Desirably, seal rings 58 and` 9V are provided between the cylinder head 5l and cylinder 52' and between the pilot 50 and the pilot-receiving opening in the housing I li. A seal Sii is also'provided for the piston rod l5 where itY passes through the head 5l.

Neglecting for the timebeing the effect of fl'uid inthe cylinder' 523,. it Will be obvious that rotative effort appliedy to: the. steering shaft 4.5

Lll) the cylinder 5E comprisesv a valve hou through the conventional steering Wheel (not shown) Will rotate the cam Il and cause the rock shaft l2 to swing about its axis. The effort required so to swing the rock shaft will be reflected as an axially directed thrust exerted by the stud 2| on one or the other of the side walls of the groove 2t. Such thrust Willtend; to. displace the earn il axially ofA itself against the force ap-plied to the cani by one or the other of the dished washers 36 acting through its associated race 34 and anti-friction bearing elements. So long as the axial thrust applied to the cam by the stud 2i is insuiilcient to overcome the opposition to cam-'movement exerted by the dished Washers,

l the cam; remains in xed axial position. However; should the axial thrust exceed the force exerted. byy the dished washer opposing it, the latter will yield and permit the cam to move axially. This movement is utilized, through means hereinafter set forth, to control the how of pressure uidttoiand from the: cylinder 521 in a mann-er which will'assist the operatorin eiectingA the: desired: movement ci the steering gear.: In this connection, it should be noted that. when the cani I7 ifs-displaced in either' directionV from its normal position. the; dishedl Washer 38a Which might' otherwise assist in effecting such movement is rendered ineiective to dorso by reason of the split spring ring. 3'8 associated.- with it, For example, assume that thestud 2l is urgingV the'cani l1 to the leftv in Figsl' and 2; such movenient' being opposed bythe dished Washer 3E at the left-hand end offthecanr. The dishedwasher 36 at the right-hand end of the cam: (Fig. 2) exertsa left-ward. force on. the carol through the associated bearing.; but assoon as the cam moves to the left, the split spring ringY 38 carries the plane Washer 3l outfof engagement with the pilot 42'. rFhe reaction of the Washer 36 atthe righthandgend ofthe. cam isthen taken by. the shoulder 3.9i; thus relieving. the. cam of. the leftward' effort 4previously exerted. upon it by the associated `dished Washer. As a result of this inodeoi operation, thecam il? isvpreloadedy and Willi not depart from its normal axial position until the force exerted on it byv the stud Z'i attains or exceeds a predetermined maximum.

The control device shown in the drawing for controlling flow of pressure huid to ani from e 55, conveniently mounted on. the sleeve is and' provided with a ported' liner $6'. A valve core E? axially. slidable within the liner 55 is connected to a lever t8 responsive to axial' movements ci the cam il. For this purpose the lever, which. is pivotally mounted intermediate its length as indicated at 68', has its lower end received in an annular groove @e in the cam-hub Se and its upper end connected to the valve core E5? through a rod l0.. For the purpose of adjusting the valve core S'L'the rod it is: desirably screwathreadledly received' therein and provided'with a lock nut 1l.

The valve liner Sii has four axially spaced ports T5, i6, Ti, and' '58. The valve core 6'!" has two lands 89 and 8l, a central passage 82, and ports 83 and 8-4 connecting the passage B'E respectively with the regions lying outwardly beyond the lands 8U and 8l and betweenthe valve body and the valve liner. The lands and 81 are spaced apartV by a distance equal to the interval between the. ports 1B and I3T and have Widths slightly less than the Widths ofV thoseV ports.

Thel ports` l5 andy Il are connected respectively through conduits 85 and 8T (Fig. l) with the inlet and outlet of a power-operated pump 88,.while the ports 18 and 18 are connected respectively through conduits 89 and 90 with the left-hand end and the right-hand end of the cylinder 52. As shown, a tank 86' is provided in conduit 86 to' accommodate for volume variations such as result from temperature changes and from the fact that the piston rod I5 modifies the crosssectional area of that portion of the cylinder through which it extends.

With the cam I1 in its normal position, the valve core 61 occupies the position indicated in Fig. 3 with the lands 80 and 8l centered respectively relative to the ports 16 and 18. vAs the lands are narrower than the ports, pressure fluid flows from the pump 88 through the conduit 81 to the valve port 11, where it divides into two streams, one flowing over the land 8i! to the port and the other owing over the land BI and through the valve-core by way of port 84, passage 82, and port S3 to the valve port 15. Combining in the valve port 15, both streams flow to the pump through the conduit 86. When the valve core is properly positioned axially of itself, the pressures respectively existing at the ports 16 and 18 and transmitted through the conduits 89 and 99 to opposite ends of the cylinder 52 will be such that their resultant effect on the piston 53 will be substantially zero. As long as this condition obtains-i. e., as long as the steering eiort is below that which will cause axial displacement of the cam I1 and consequent movement of the valve core 61-the steering gear operates under manual control, uid displaced by movements of the piston 53 being, in eifect, transferred from one end of the cylinder to the other through the valve.

When the steering effort becomes great enough to cause axial displacement of the cam I1, the valve core 61 is displaced and iiuid under pressure is supplied to the cylinder 52 to aid the operator in overcoming the steering effort. For example, assume that the steering shaft 45 is being rotated manually in a direction to cause clockwise swinging o f the shaft I2. Under that condition, the stud 2l will exert a rightward effort on the cam I1; and if that eiort exceeds the preloading of the cam, the cam will move to the right and cause the valve core 61 to move to the left. Leftward movement of the valve core will decrease the 'resistance to fluid flow from the valve port 11 to the port 16 and from the port 18 through the valve core to the port 15, and will increase the resistance to now from the port 18 to the exhaust port 15 and from the supply porty 1 1 to the port 18. As a result, the pressure in the left-hand lend of the cylinder 52 will increase and that in the right-hand end will decrease, thus forcing the piston 53 to the right and applying. clockwise effort to the arm I8 and shaft I2. If the displacement of the valve core 61 is great enough, the land 88 will shut oi .all ow from the port 16 to the exhaust port 15 and the land 8| will shut off all flow from the supply port 11 to the port 1B. By appropriately locating the pivot 68 of and the valve core 61 to the right, thus increasing 'pressure in the right-hand end of the cylinder Iii 52 and decreasing pressure in the left-hand end,

as a result of which the piston 53 will be forced to the left and the block 23 will exert a counterclockwise eiort on the arm I8.

In order to obtain the most satisfactory results in operation of the device, it is essential that the valve core 51 be accurately positioned to produce balanced pressures in the cylinder 52 whenever the cam occupies its normal position. To aid in attaining the proper adjustment of the Valve core B1, the lands and SI are accurately located with respect to the machined outer end face 92 of the valve core, and the ports in the liner 58 are accurately located from the machined outer end face 93 of the liner, the arrangement being such .with a transverse slot 94 adapted to receive a .screw-driver or equivalent tool for use in rotating the valve core on the threaded end of the rod 10. For the purpose of projecting the valve mechanism, we may provide a removable cover 95 adapted for attachment to the outer end ofthe valve body 65.

In adjusting the device for operation after the valve body 65 has been mounted on the sleeve 43 and the sleeve has been secured in position on the housing Ill, the steering shaft l5 is rotated if necessary to relieve all steering effort and thus insure that the cam I1 will occupy its normal position, the cover 95 on the valve body is removed, the lock nut 1I is loosened, and the valve core 61 is rotated on the threads of the rod 10 until its outer face 92 is accurately iiush with the outer face 93 of the liner 68, whereupon the lock nut 1I is tightened and the cover 95 replaced.

Desirably, the two .openings 32 and 39 in the housing' I0 are identical, so that either may receive the sleeve-pilot 42 while the other receives the spacer 40 and is closed by the cap 4I. It is also desirable that the housing I9 be provided with identical openings 49 located in alignment in opposite sides of the casing and adapted alternatively to receive the pilot 5l) of the cylinder 52. By so constructing the housing, the cylinder 52 and the sleeve 43 may be placed on either side thereof, and the sleeve cylinder may either be on the same or on opposite sides of the casing with respect to each other. The possibilities in respect to the alternative positioning of the sleeve 43 and cylinder 52 greatly increase the flexibility of installation of the steering gear. The opening 49 on the side of the casing I9 remote from the cylinder 52 may be covered with a removable cap 91. To facilitate interchange 'in the position of the cap 91 and the hydraulic cylinder, the cap and the collar 5d are drilled in corresponding patterns for the passage of the screws 51 which secure them to the sides of the housing. The same Varrangement may be einployed in the case of the cap 4I and the sleeveflange 44, which are drilled in similar patterns for the passage of screws 98 that extend into threaded openings in the housing IE. By appropriately locating the holes which receive the 'screws 98, the sleeve 43 may be mounted in a plurality of different positions of angular adjustment about the axis of the openings 32 and 33, thus making it possible to position the valve 7 65f'to best advantage. Since the cylinder 52 is rotatable relatively to the collar 54, it can be oriented in any position about its axis.v

Although we have shown the hydraulic control valve and the steering shaft @l as operatively connected to the same end of the cam il', it is to be understood that such arrangement is not essential.

In Fig. 6 we have illustrated, for one end or" the cam il, a modiiied form of means for rotatably supporting and yieldingly centering such cam. In the arrangement there shown, the cam-body is provided with plain end portions rotatably received in bearing openings le! provided in the side walls of the housing Iii and adapted to support the cam against radial loads, while a simple thrust-type anti-friction bearing E34- is provided for each end oi the cam for the transmission of axial loads. Between the bearing I 3e and a shoulder 62 formed by the end of the cam-body there is disposed an axially movable collar H63 having an annular series or" openings each adapted to receive a compression spring itil acting on the bearing i3d and urging it axially outward. Such outward movement of the bearing under the forces exerted on it by the several springs Ult is limited by a split spring ring E38 on the associated cam-hub. As in the arrangement shown in Fig. 1, abutments, such as the pilot 42 of sleeve M3, position the assembly of the cam, collar ist, springs lil-", and bearing i3d axially of itself in such a way that the springs all at opposite ends of the cam hold it with predetermined force in its normal position.

Still another modified form of cam-locating means is illustrated in Fig. 7. Here the antifriction bearing is of the combined radial and thrust type, the outer race M being slidably supported in the housing ie, as the race i is supported in Fig. l. The dished washer 35 oi" Figs. l and 2 is replaced with an annular series of compression springs 23@ seated in recesses in the outer face of the race and bearing against a plane washer @outward movement of the washer relative to the cam is limited by a split spring ring 23S, whilev its outward movement relative to the casing is limited by an abutment such as the pilot on the sleeve 243.

in Fig. s, we have illustrated a modified form or" for preserving paralielism between the rock shaft i2 and the axis of the pin '-.vh oarr'es the block As there shown, 'the pin its, on wh' the block 23 is mounted, through and beyond the piston-rod head i into a bearing sli ably received in a groove il'i formed in the housing at the side of the guide-way for the piston-rod head Hd. if it is deemed necessary to bearing surfaces between the block MJS and the piston-rod head Elfi, the hole in the latter through which the pin 52d passes be counterbored to receive a circular boss U28 on the block i.

We claim as our invention:

l. ln a power-operated steering gear, a housing having a side wall provided with an opening, a cam. means rotatably supporting said cam in said housing and in alignment with said opening, a rock shaft supported in said housing and having a laterally projecting arm cti-operating with said cam, said cam being generally helical whereby the effort transmitted between it and the shaft will react on the' Cam. with an axial component, said cam-supportingmeans permitting a limited axial movement of the cam, yielding means biasing. the cam toward a normal position intermediate its limits of axial movement, a support, a manually rotatable steering shaft mounted in said support in xed axial position, means for securing said support to said housing with the steering shaft and Cam in coaxial relation, means interconnecting said cam and shaft for joint rotation while permitting axial movement of the cam, and power-operated means including a control device responsive to axial movements of the cam for rotating said rook shaft, said control device being mounted on said support.

2. In a power-operated steering gear, a housing having aY sidewall provided with an opening, a cam, means rotatably supporting said cam in said housing and in alignment with said opening, a rock shait supported in said housing and having a laterally projecting arm co-operating with said cam, said cam being generally helical whereby the eiort transmitted between it and the shaft will react on the cam with an axial component, said cam-supporting means permitting a limited axial movement of the cam, yielding means biasing the cam toward a normal position. intermediate its limits of axial movement, a support, a manually rotatable steering shaft mounted in said support in fixed axial position, means for securing said support tor said housing with the steering shaft and cam in coaxial relation, means interconnecting said cam and shaft for joint rotation while permitting axial movement of the cam, and power-operated means including a control device responsive to axial movements of the cam for rotating said rock shaft.

3. The invention set forth in claim 2 with the addition that. said side wall is one of two spaced, opposite walls each provided vwith an opening alignedv with said. cam, said cam being reversible in its supporting means, and said supportsecuringV means being adapted to secure said support alternatively at either side or" said housing.

4i. The invention set forth in claim 2 with the addition that said. support has ay pilot portion receivable in said opening.

5. In a power-operated steering gear, a housing having spaced, opposite side walls provided with rst and secondv pairs of aligned openings, a manually rotatable cam, means in said housing for rotatably supporting said cam between the openings or" said rst pair and in alignment therewith, said. cam. having an axially extending hub. at one end and being reversible in said cam-supporting means whereby said hub may extend outwardly alternatively through either of the aligned` openings, a slide, means in said housing mounting said slide for reciprocation along a path. between said side walls and paraliel to the common axis of the second pair of openings, a roel: shaft mounted in said housing between and with its axis in a plane perpendicular to the cam-axis and to the path of movement of said slide, said rock shaft having rigid with it arms operatively connected respectively to said cam and slide, said cam being generally helical whereby effort transmitted between it and the rook-shaft will react on the cam with an axial component, said cam-supportingV means permitting a limited axial movement of said cam. means biasing said cani toward a normal position intermediate the limits of such axialy movement and yieldable torpermit axial movement of the cam, a hydraulic cylinder, means for mounting said cylinder alternatively on either side of said housing in alignment with said second pair of openings, a piston in said cylinder, a pistonrod interconnecting said piston and slide and extending through the adjacent one'of the openings aligned with the cylinder, means including a source of fluid under pressure and a control valve for forcing said piston alternatively in either direction, means for mounting said valve alternatively on opposite sides of said housing for co-operation with the cam-hub, and means operatively interconnecting the valve and camhub.

6. In a power-operated steering gear, a housing having a pair of spaced, opposite side Walls provided with aligned openings, a rockshaft mounted in said housing on an axis displaced from that of said openings, a slide, means supporting said slide for reciprocating motion along a path extending in the same direction as the common axis of said openings, an operative connection between said slide and rock shaft, a hydraulic cylinder, a piston therein, a piston rod operatively interconnecting the piston and slide, and means for securing said cylinder alternatively on either side of said housing with said piston rod extending through the adjacent one of said openings.

'7. The invention claimed in claim 6 with 'the addition that said cylinder has a head provided with a pilot portion alternatively receivable in either of said openings.

8. In a power-operated steering gear, a rock shaft, manually operated means for rotating said rock shaft, hydraulic means for rotating said rock shaft, said hydraulic means including a valve comprising a cylinder and an axially slidable core therein for controlling rotation of the rock shaft by said hydraulic means, said core and cylinder having end faces so located that when they are in a predetermined relative axial position said valve occupies a neutral position in which it renders the hydraulic means ineffective to rotate the rock shaft, and a connection between said manually operated means and said valve core for moving said valve core from its neutral position when the effort transmitted between the rock shaft and manually operated means exceeds a predetermined value, said connection being adjustable to permit the end faces of said valve-core and cylinder to be brought into said predetermined relative axial position.

9. In a power-operated steering gear, a rock shaft, manually operated means for rotating said rock shaft, hydraulic means for rotating said rock shaft, said hydraulic means includingr a Valve comprising a cylinder and an axially slidable core therein for controlling rotation of the rock shaft by said hydraulic means, said core and cylinder having end faces so located that when they are flush with each other said valve occupies a neutral position in which it renders the hydraulic means ineffective to rotate the rock shaft, and a connection between said manually g operated means and said valve core for moving said valve core from its neutral position when the eifort transmitted between-the rock shaft and manually operated ymeans exceeds a predetermined value, said connection being adjustable to permit the end faces of said valve-core and cylinder to be brought into said flush relationship.

10. In a power-operated steering gear, a housing, a manually rotatable generally helical cam supported in said housing for rotative and limited axial mo-vement, an operative connection between said cam and rock-shaft so constructed and arranged that effort transmitted between the cam and shaft reacts with an axial component on the cam, a pair of thrust members movable axially of the cam, yielding means acting between the cam and thrust members and urging the thrust members in opposite axial directions, abutments on the cam to limit movement of the thrust members relative to the cam under the influence of 'the yielding means, abutments on the housing for limiting movement of said thrust members relative to the housing, power-operated means for r0- tating the rock shaft, and a control device for said power-operated means responsive to axial movement of the cam.

1l. In a power-operated steering gear, a housing, a manually-rotatable generally helical cam supported in said housing for rotative and limited axial movement, an operative connection between. said cam and rock-shaft so constructed and arranged that effort transmitted between the cam and shaft reacts with an axial component on the cam, a pair of springs acting oppositely on the cam and reacting on the housing to bias the cam toward a normal position intermediate its range of axial movement, means effective when the cam moves against the force exerted on it by either spring to transfer from the housing to the cam the reaction of the other spring, powervoperated means for rotating the rock shaft, and a control device for said power-operated means responsive to axial movement of the cam.

12. The invention set forth in claim 11 with the addition of an anti-friction bearing transmitting the biasing effort of each spring to the cam.

13. In a power-operated steering gear, a housing, a rock-shaft mounted therein, said housing having a guide-way offset from'saidV shaft and extending in a plane perpendicular thereto, a slide reciprocable in said guide-way, said shaft being provided with a rigid arm projecting radially from the shaft at one side of said guide-way and provided with a radially extending opening, forcetransmitting means extending laterally from said slide into said opening for operatively interconnecting the slide and arm, power-operated means for moving said slide along said guide-Way, said slide and guide-way being of circular cross-section', and means acting between said slide and housing for preventing rotation of the slide in the guide-way.

14. In a power-operated steering gear, a housing, said housing having a wall provided with an opening, a hydraulic cylinder having an open end, a removable cylinder-head` having end portions respectively received in said housing-opening and in the open end of said cylinder and provided intermediately with an exterior annular flange, a collar surrounding said cylinder, means limiting movement of said collar along said cylinder toward said housing, means for forcing said collar toward the housing to clamp the flange on said head between the housing and the adjacent end of the cylinder, said head having a central opening, a piston in said cylinder, and a piston rod extending through said central opening into said housing for connection to a movable element.

15. In a power operated steering gear, a housing, a manually rotated cam, means rotatably supporting said cam in said housing, a rock shaft supported in said housing and having a laterally projecting arm co-operatingwith said cam, said cam being generally helical whereby the effort transmitted between it andthe rock shaft will react on the cam with an axial component, said cam-supporting means permitting a vlimited axial movement of the cam, a motor connected to said rook shaft for rotatingit alternatively in either direction, a control device for said motor, and a connection between said cam and control device whereby axial movement of the cam will cause the control device to actuate the motor, said connection being adjustable to vary the condition of the control device for any axial position of the cam.

References Cited n the le of this patent UNITED STATES PATENTS Number 12 Number Name Date' 1,633,209 Henninger June 21, 192'7 1,790,620 Davis Jan. '27, 1931 1,937,470 Davis Nov. 28, 1933 2,053,272 Eaton Sept. k8, 1936 2,065,513 Centervall Dee. 29, 1936 2,114,165 Cochran Apr. 12, 1938 2,213,271 Davis Sept. 3, 1940 2,362,930 Robbins Nov. 14, 1944 2,391,819 Creson Dec. 25, 1945 2,410,049 Davis Oct. 29, '1946 2,433,209 Creson et al. Dec. 30, 1947 2,605,854; MacDuiT Aug."5, 1952 OTHER REFERENCES Product Engineering, vol. 22, Issue No. '1, page 112, Jan. 1951. 

